International Ground-to-Air Signaling Code

How to Send Clear Signals to Passing Aircraft If You're Ever Stranded or Injured in the Wilderness

For those of us who head out into remote locations to hike, camp, hunt, fish, or practice survival skills, the possibility of becoming stranded is always a consideration. This nightmarish situation is more likely than we might want to admit — a study in the Journal of Wilderness and Environmental Medicine showed an average of 11.2 search-and-rescue (SAR) incidents each day between 1992 and 2007 in the U.S. National Park system alone. The study also found that without aid from SAR teams, “1 in 5 (20%) of those requesting SAR assistance would be a fatality,” and that’s just among those who were able to call for help.

In a truly remote location, a passing aircraft may be your best hope of rescue.

Whether it’s due to a broken bone, sudden illness, severe weather, animal attack, or some other dire emergency, there are many instances where self-rescue may not be possible. We often over-confidently assume we’ll be able to make it to safety under our own power, but if something catastrophic happens, you’d better know how to call for help. We’ve previously discussed signal mirrors, smoke canisters, and electronic beacons, but there’s an even more basic system you should know: the international ground-to-air signaling code.

This standard system is designed to send a clear visual message to any aircraft that might pass your location. Here’s a quick reference guide from FarAim.org on the five signals you should know:

X can also be interpreted as “unable to proceed” — in other words, V can be used when you need help but are still mobile, while X indicates that you’re severely injured and cannot move. Y and N may be used to respond if the aircraft uses a loudspeaker to provide instructions.

These letters should be constructed on a clear patch of ground, with as much contrast between the symbols and backdrop as possible. Bright strips of parachute or pieces of dark wood on a light sand beach are good examples of this principle. In snow, this can be accomplished by walking or dragging an object to create a depression in the shape of the symbol. Also, remember to make the symbol as large as you can — at least 10 feet wide is recommended.

If a pilot spots your distress signal, the internationally-accepted acknowledgment is to rock the plane’s wings from side to side. In low-light conditions, the aircraft may flash green exterior lights, or turn its landing lights on and off two times. Refer to the following figure from the U.S. Army Field Survival Guide for a visual depiction.